Pneumosinus dilatans of the spheno-ethmoidal complex associated with hypovitaminosis D causing bilateral optic canal stenosis.

Introduction: Pneumosinus dilatans (PSD) is a rare disorder of undetermined etiology characterized by expansion of the paranasal sinuses without bony erosion. Of the few cases of PSD described in indexed pediatric literature, there has been no reported case of this disorder presenting with optic canal stenosis in the setting of a vitamin deficiency.
Case Material: A 12-year-old girl presented with a 3-month history of progressive, painless, and asymmetric visual deterioration in her eyes. MRI showed prominent perioptic CSF spaces bilaterally and mild atrophy of both the optic nerves. CT head showed hyperpneumatization of the sphenoethmoidal air cells and both anterior clinoid processes with the optic nerves contained within narrowed intact bony canals. Blood investigations showed reduced vitamin D levels, and a subsequent skeletal survey showed diffuse osteopenia. She underwent endoscopic sphenoidotomy and bilateral decompression of the optic nerves. Following surgery, she reported improvement of vision in her left eye. She was started on vitamin D supplements for the endocrine abnormality. At a follow-up visit 6 months later, her visual acuity in both her eyes had improved.
Conclusion: Pneumosinus dilatans is an unusual cause of progressive optic nerve dysfunction in the pediatric population. In the absence of any associated intracranial pathologies, conditions like hypovitamosis D should be ruled out.